How to do a delphi-like form layout?

Delphi's layout system is an absolute layout system where you anchor controls to a fixed distance from any edge. If you anchor a control to the right edge, it will change its x coordinate when the container resizes. When you anchor a control to both edges, it will keep both its x coordinate and its distance from the right edge.

In the middle row the "Valid From" and "Valid Until" date fields are anchored only to the right edge, so they will not resize, only change their x position. The "Customer" field however is anchored to both edges, so it will resize.